Apparatus for transmitting motion under the positive control of an escapement mechanism



July 28, 1959 c. F. WEBB APPARATUS FOR TRANSMITTING MOTION UNDER THEPOSITIVE CONTROL OF AN ESCAPEMENT MECHANISM Filed Aug. 18, 1954APPARATUS FOR TRANSMITTING MOTION UNDER THE POSITIVE CONTROL OF ANESCAPE'MENT MEG: M

Application August 18, 1954, Serial No. 450,746

Claims priority, application Great Britain September '1, 1953 5 Claims.(Cl. 18537) This invention is for improvements relating to apparatus fortransmitting motion under the positive control of an escapementmechanism.

In a conventional spring driven clock the only normal purpose is toindicate the passage of time. In such case the value of the forceapplied to a train of wheels is determined by the frictional and otherconsiderations in the operation of the escapement, so that a balancewheel or pendulum is supplied with approximately the correct amount ofenergy to maintain it in oscillation.

It is common for ancillary duties to be performed by the same mechanism,such as the release of striking mechanism, which usually modify onlyslightly the force acting on the escapement, and, except in apparatus ofspecial precision, do not detrimentally affect the performance or wearof the escapement.

In certain time-controlled apparatus however, a relatively high power inthe driving spring is necessary to per form other duties, as for examplein a taximeter, in which the motive force must be adequate for theoperation of the fare-computing and registering machanism and may thusbe more than ten times the optimum amount for maintaining the clockescapement in operation. Furthermore, such registration in terms of timeis conditional on the prevailing circumstances affecting the vehicle,whereby during the greater part of each journey the whole of the excessdriving force in the spring must be restrained by the escapement withconsequent difficulties arising from wear and inefiicient performance ofthe clock.

The force required to operate the lever and balance wheel efiicientlymay for example be two or three grammes on the periphery of the escapewheel, but for the reasons stated it may actually be 20 or 30 grammesattimes. Even when the registering mechanism is being driven the value ofthe force drawn from the clock may vary considerably, so that irregularpressure is exerted on the escapement.

The object of the present invention is to isolate from the escapementall such fluctuations and excess by maintaining a minimum and constanttorque on the escape wheel.

The invention thus relates to apparatus, such as for example the clockof a taximeter, for transmitting rotary motion to a torque output shaftunder the control of an escapement mechanism, and in which the torquerequired to operate the escapement mechanism is small compared to thetorque (which may be variable) which the apparatus provides at itstorque output. The invention provides in such apparatus means forreducing the torque applied to the escapement to a low, constant valueappropriate to the small force required to drive the escapement.

2,896,747 Patented July 28, 1959 These means are located between thetorque output oh the apparatus and the escapement and comprise a springwhich is adapted for torsional deflection and which is coupled between adriving and driven member. These are connected respectively to thetorque input and torque output ends of the spring just mentioned. Thedriving member is driven by the torque transmitted in the part of theapparatus between the torque input end thereof and the torque reducingmeans, and the driven member is driven by the torque of the spring. Astationary member is located in such proximity to the torque input endof the spring that a very small amount of deflection movement of thespring causes the torque input end thereof to bind upon the stationarymember with resulting restraint upon the driving member from tensioningthe rest of the spring above a predetermined value sufficient only toproduce at the escapement mechanism the force necessary to cause thatmechanism to function.

A preferred construction, as applied to the clock of a taximeter, isshown in the accompanying drawings, in which:

Figure l is a side elevation of a spring driven clock mechanism in whichfor clarity the gear stages are shown extended in a single plane;

Figure 2 is a fragmentary view, drawn on a larger scale than Figure 1,showing the constructional details of the torque reducing means as abovereferred to of the apparatus; and

Figure 3 is a perspective view of the parts shown in Figure 2.

Referring to Figure l, a frame 1 supports a spring barrel 2 and a trainof wheels and pinions 3, 4, 5, 6, 7, 8, 9, and the escape wheel 10,which is controlled by a lever 11 and a balance wheel 12.

At some convenient stage in the train of gearing, for example at theshaft of pinion 5, the spindle may be extended at 13 to provide anoutput power shaft in order to deliver the force and motion forregistration or other purposes as required. At a convenient stagebetween this output shaft 13 and the escapement, say on the shaft ofpinion 7, the automatic control of excess torque is introduced. InFigures 2 and 3 it will be seen that the wheel 8 is not directlyattached to the shaft 01 the pinion 7, but is freely mounted for limitedrotation thereon, the pinion having an arm 14 attached which passesthrough an aperture in wheel 8. Also freely mounted on the shaft of thepinion 7 is a bush 15 which is held against rotation by an arm 16locating against some portion of the frame 1.

The stationary bush 15 and the boss or hub of the moving wheel 8 areadjacent, and of equal diameter. Both are freely encircled by the coilsof a spiral spring 17, one end of which is connected to the arm 14 andthe other to the wheel 8. The first mentioned end of the spring 17 formsthe torque input end thereof and the other the torque output end. Theproportions of the spring are such that after a partial rotation hasbeen given to the arm 14 the coils contract upon and tend to grip thebush 15, the tensional torque of the spring 17 at that instant providingthe desired torque on the wheel 8. Only the first one or two coils ofthe spring at the torque input end thereof bind upon the stationary bush15, the remaining coils remaining free to transmit and maintain thepredetermined torque on the wheel.

In the process of driving the escapement, the intermittent movement ofthe Wheel 8 momentarily (i.e. at each escape of the escape wheel)enlarges the diameter of the spring, causing a partial release of thegrip thereof upon the bush at the torque input end of the spring,enabling the arm 14 to follow up and restore the grip. In practice thedevice is so sensitive that less than 1 degree of angular movement ofthe wheel 8 is sutficient to release the restraint and enable the arm 14to follow up. The degree of grip of the first one or two coils alsobecomes automatically adjusted to the driving torque on the shaft of thepinion 7, resulting in a substantially constant torque x on theescapement over a range of at least x in the applied force.

As the torque control is applied after the point 13 in the gear trainfrom which the registering power is delivered, the device imposes nolimitation on the full power of the clock being available at shaft 13whenever required.

It is only when such registering power is not being fully withdrawn (andtherefore tends to increase the torque on wheel 10 above the value x)that the excess is restrained. The value of the restraint at any giveninstant can be expressed as R=pt-x, where:

p=total available power of clock.

t=power being transmitted externally.

x=power being expended internally to operate the escapement.

The scope of the invention is not limited to the exact constructionalform of the invention illustrated in the drawings. For example, thestationary bush 15 may be of a larger diameter internally than the shaft7 and be fixed directly to the frame 1 in concentric relation to theshaft. In this case the bush would not be guided on the shaft as it isin the construction illustrated in the drawings. Also the cylindricalmember constituted by the bush 15 in the construction illustrated may beof tubular formation with the coil spring extending into the tube fromone end thereof, the arrangement being such that in the operation of thetorque reducing device the spring expands into binding engagement withthe bore of the tube, the stationary member being in this sense locatedaround the coils of the spring, whereas in the case of the constructionillustrated it is located within the coils of the spring. The particularconstruction illustrated, however, enables the dimensional and torsionalvalues of the component parts of the device to be predetermined with ahigh degree of accuracy and at the same time the complete device to bedesigned as a self-contained unit ready for assembly in a clockmechanism. For this reason the construction illustrated may be regardedas a generally preferred form of the invention.

An arrangement in accordance with this invention is specially suitablein the case of an apparatus for providing power transmission controlledby time measurement within the same piece of apparatus, as in the casedescribed above and illustrated in the drawings of a clock of ataximeter, but it can also be employed in any apparatus where at thetorque output end thereof a substantially constant torque or motion isrequired derived from a source of power applied at the torque input endof the apparatus which is greater in terms of torque transmission thanthe torque output of the apparatus or which is of non-uniform speed.

What I claim as my invention and desire to secure by Letters Patent ofthe United States is:

1. Apparatus for developing uniform rotary motion comprising a train ofgears, a spring coupled to one end of said train, an escapement coupledto the other end of said train, and means to minimize variations intorque in said gear train at the end thereof adjacent said escapement,said means including two gears of said train mounted coaxially of eachother, a stationary barrel mounted coaxially of said two gears, a spiralspring fastened at one end to a point fixed with respect to one of saidtwo gears and at the other end to a point fixed with respect to theother of said two gears, said spiral spring having some of its coilsdisposed about said barrel, and means to limit relative rotation of saidtwo gears to a fraction of a revolution.

2. A clockwork motor for driving an apparatus which imposes afluctuating torque load upon the motor, said motor comprising a train ofgears, a main spring coupled to one end of said train, an output powershaft coupled to a gear in said train intermediate the ends thereof, anescapement coupled to the other end of said train, and means to minimizevariations in torque in said gear train at the end thereof adjacent saidescapement due to fluctuations of load on said power output shaft, saidmeans comprising two gears disposed in said train between said poweroutput shaft and said escapement, said two gears being mounted coaxiallyof each other, a stationary barrel mounted coaxially of said two gears,a spiral spring having one end fastened at a point fixed with respect toone of said two gears and the other end fastened at a point fixed withrespect to the other of said two gears, said spiral spring having someof its coils disposed about said barrel, and means to limit relativerotation of said two gears to a fraction of a revolution.

3. A clockwork motor for driving an apparatus which imposes afluctuating torque load upon the said motor, said motor comprising atrain of gears, a main spring coupled to one end of said train, anescapement coupled to the other end of said train, an output shaftcoupled to one of the gears of said train intermediate the ends thereof,and means to minimize variations in torque in said gear train at the endthereof adjacent said escapement, said means comprising two gearsdisposed in said train between said shaft and said escapement, said twogears being mounted coaxially of each other, a stationary barrel mountedcoaxially of said two gears, the one of said two gears remote in saidtrain from said spring having an arcuate aperture therein, the other ofsaid two gears being disposed on the side of said one gear opposite saidbarrel, an arm fast to said other gear extending through said aperture,and a spiral spring fastened at one end to said arm and at the other endto said one gear, said spiral spring having a fraction of its coilsdisposed about said barrel.

4. A clockwork motor for driving an apparatus which imposes afluctuating torque load on the motor, said motor comprising a train ofgears, a main spring coupled to one end of said train, an escapementcoupled to the other end of said train, an output shaft coupled to agear in said train intermediate the ends thereof, and means to minimizevariations in torque in said gear train at the end thereof adjacent saidescapement due to fluctuations of load on said power output shaft, saidmeans comprising two gears disposed in said train between the gear towhich said shaft is coupled and said escapement, said two gears beingmounted coaxially of each other, a stationary barrel mounted coaxiallyof said two gears, the one of said two gears remote in said train fromsaid spring having an arcuate aperture therein and having an axiallyextending hub thereon adjacent said barrel, the other of said two gearsbeing disposed on the side of said one gear opposite said barrel, an armfast to said other gear extending through said aperture beyond said hub,and a spiral spring fastened at one end to said arm and at the other endto said one gear, said spiral spring having a fraction of its coilsdisposed about said barrel and a fraction of its coils disposed aboutsaid hub.

5. A clockwork motor for driving an apparatus which imposes a widelyfluctuating torque load upon the motor, said motor comprising a train ofgears, a main spring coupled to one end of said train, an escapementmechanism coupled to the other end of said train, said apparatus beingexternal to said train, one of the gears of the train, located betweensaid main spring and said escapement mechanism, having means forcoupling the train in driving relation to said apparatus, and means tomaintain the 5 torque in said gear train, at the end thereof adjacentsaid escapement mechanism, substantially constant as the torque loadupon the motor, imposed thereupon by said apparatus, fluctuates, saidmeans including a first gear, a second gear mounted coaxially of saidfirst gear and in driving relation thereto, said first and second gearsforming successive gear elements in said gear train and being disposedin said gear train between said one gear and said escapement, astationary barrel mounted coaxially of said first and second gears and aspiral spring fastened at one end to a point fixed with respect to saidfirst gear and at the other end to a point fixed with respect to saidsecond gear, said spiral spring having some of its coils adjacent itsfirst mentioned end disposed about said barrel so as alternately to bindthereon and un'bind therefrom with motion of said escapement mechanism.

References Cited in the file of this patent UNITED STATES PATENTS

